@Max - yes they are fascinating to watch. As coincidence would have it I had to move a stationery cupboard yesterday to make room for an equipment cabinet and inside the cupboard I found a bottle of Rotring drawing ink. Now if I can find my pens I can get the machine working properly (previously tried it with a small felt tip pen).

I thought of mounting a small laser in the holder to mark text on things, but it would have to be a very light, very powerful laser. Or get a very small motor and a milling tip and modify the innards, to mill small PCBs. Neither is very practical though. ANyone else got any ideas on what you can do with these cute dinosaurs?

I used to do my schematics and PCBs on a Roland A3 size plotter. For the schematics I used HP fibre tipped pens, but the PCBs were plotted with Rotring pens on tracing paper using Indian ink(?). I still have the kit at home, I must check if it was called that. The CAD software was Autocad. Really- I used to do my boards using a package that was an overlay of AutoCAD. I could write AutoCAD scripts in my head, but that is another story.

Plotting a Eurocard size board would take ~2-4hours a layer because the pens had to move slowly to allow the ink to flow. Often the pen would stop working. I developed a technique to allow a continuation of the plot rather than starting from scratch (pun intended, if you ever had any experience with those pens). The probablity of a pen failing increased in direct proportion to the time taken to plot. It was not possible to start the Autocad plot from a particular point, but it was possible to pause it. Pausing was needed to refill the ink and sometimes you could also get a feel if the pen needed a clean.

So I would restart the plot and allow it to plot without a pen until it got close to the point where it stopped. I would then pause, insert the pen and allowed the plot to continue. Re-registration of the plotter was excellent.

One of the secrets of more reliable operation was to soak the pen in a special Rotring Solution inside a special Rotring container (still have it) when not in use. Never let the pen dry out! Getting a pen started was also an issue, shaking it up and down and listening for the click-click of the internal pen tip stopper. When you didn't hear it, you shook harder and.... splat! Spit was also a technique to start the flow.

You could also get a larger reservoir for those longer plots, if you were optimistic enough that it wouldn't stop.

@David: Re Slide 10: ...Lettering machine -- a small rectangular case with a keyboard and an arm holding a drawing pen. I was lucky enough to get two of these in my pickings from our drawing office chuck-outs and they both work

Wow! I loved the videos in your blog -- I would love to see your machines in action!

Re Slide 5 -- Compasses to draw circles or arcs with lead or pens. These look to be really good quality -- I've been amazed by the poor quality of a couple of different compasses I've purchased recently from places like Staples.